Could Alzheimer’s disease actually be a form of diabetes in the brain?

A recent issue of New Scientist posed the theory in a cover story illustrated with an ominous image of a cracked chocolate brain.

“It is well known that bad diets can trigger obesity and diabetes,” the magazine warned in an editorial. “There is growing evidence that they trigger Alzheimer’s disease too, and some researchers now see it as just another form of diabetes.”

Chief among those researchers is Brown University neuropathologist Suzanne de la Monte, who found that in Alzheimer’s disease, the brain’s ability to metabolize sugar is reduced, creating what she calls “diabetes in the brain.”

“Consequently, the brain cells practically starve to death,” she said.

De la Monte turned to statistical evidence to look for a cause, and found a connection: a fivefold increase (from 1970 to 2005) in U.S. consumption of fast food and processed meats and, over the same period of time, a fivefold increase in rates of Alzheimer’s, diabetes and fatty liver disease among people 55 and older.

De la Monte blames the high-fat, high-sugar, highly processed American diet, and in particular, nitrites, an additive used in meats and processed foods for flavor and coloring.

Nitrites are converted to nitrosamines in the body, according to de la Monte, and “we have reasonable evidence that human exposure to nitrosamines is at the root cause of not only Alzheimer’s but several other insulin-resistance diseases, including Type 2 diabetes,” she said.

Dr. John Hart, medical science director for the Center for BrainHealth at the University of Texas at Dallas, says de la Monte’s theory is intriguing, but researchers aren’t yelling “Eureka!” just yet. He thinks it’s just one possible piece of the Alzheimer’s puzzle.

“There are other factors that we are chasing down, and have been chasing down for years, including this one, as possible treatment options,” Hart says. Genetics seems to play a role in Alzheimer’s, as does inflammation, he said, adding that most researchers suspect that the disease may be “multifactorial.”

There is a clear statistical link between diabetes and dementia, with Alzheimer’s being the most common form of dementia, but it doesn’t necessarily follow that Alzheimer’s is a form of diabetes, he says.

Impaired glucose metabolism may be part of the puzzle, but “a more obvious explanation, from a research point of view, is that people who are diabetic get tiny clots in their arteries,” Hart says. “In some, it affects the kidneys, in some it causes blindness, but in a lot of individuals you get these clots, little small strokes, in the brain, and it’s very clear that leads to an increased chance of getting dementia, including Alzheimer’s.”

Having studied Alzheimer’s since graduating from medical school in 1983, Hart says a clear cause of the disease remains elusive. The hallmark abnormalities of Alzheimer’s are found in the brain: deposits of plaque (the protein fragment beta-amyloid) and tangles (twisted strands of the protein tau), as well as evidence of damage to and death of nerve cells.

But it’s not even obvious whether those are the causes or the consequences of Alzheimer’s.

According to the Alzheimer’s Association, 1 in 8 older Americans has Alzheimer’s disease, and it is the sixth-leading cause of death in the U.S. The cost of caring for Alzheimer’s patients is expected to run around $200 billion in 2012, and that doesn’t include the unpaid care provided by loved ones.

While the researchers sort this one out, you can’t go wrong by following de la Monte’s key recommendation: skipping high-fat, high-sugar, highly processed foods for healthier foods such as fish, fresh fruits and vegetables. Other evidence-based ways to reduce your risk of Alzheimer’s include avoiding smoking, staying physically and mentally active, and if you have diabetes or high blood pressure, controlling them as best you can.

“Nobody likes doing them, but exercising and eating healthfully really does make a difference,” Hart said.

Mary Jacobs is a Dallas freelance writer.

The diabetes-dementia link

Doctors don’t know what causes Alzheimer’s or exactly how it or other forms of dementia are linked to diabetes. It is clear that insulin resistance, high blood sugar or diabetes may harm the brain in several ways:

Insulin resistance and Type 2 diabetes increase the risk of heart disease and stroke; damaged blood vessels in the brain may contribute to Alzheimer’s disease.

Brain cells use high levels of energy; the inability to absorb sugar may damage these cells.

Too much insulin may upset the balance of chemicals in the brain, which could help trigger Alzheimer’s.

High blood sugar causes inflammation, which may damage brain cells and contribute to the development of Alzheimer’s.